The present invention relates to take-up reels of the type for winding and paying out an elongated flexible member such as a cable, cord or hose, and which automatically rewind the flexible member when it is released.
The art is replete with apparatus in which a flexible member such as a cable, rope, hose, electrical cord or the like is wound about a take-up reel for storage when not in use, and which is paid out by unwinding from the take-up reel to the appropriate length as required. A popular application for this arrangement is use of a flexible hose for carrying air, water, oil, or grease from a reservoir to a dispensing nozzle at an automobile service station. For example, in the typical automobile service station, air is delivered from a compressor tank through a long pipe to a spring-loaded take-up reel about which is stored a length of tubular air hose. When air is needed, the air hose is pulled from the reel until the desired length is paid out. When the air hose is no longer in use, the end is released and a torsional spring acting on the hose reel rewinds the hose onto the reel.
The torque exerted by the torsional spring on the take-up reel causes the take-up reel, and with it the payed-out hose, to accelerate as the hose is taken up, with result that the terminal velocity of the hose may be quite high as the last bit of hose is retracted. The sudden stop of the mechanism when the end of the hose is reached can cause damage to the rewind mechanism and/or the hose. Moreover, it would be advantageous to reduce the possibility that the whipping action occurring as a result of the uncontrolled rewinding speed might cause personal injury. Various braking mechanisms have been proposed for automatically limiting the rewind rate of the take-up reel. For example, U.S. Pat. No. 4,446,884 to Rader, Jr. proposes use of a viscous damping mechanism coupled between the spool and its support shaft. Being a viscous damper, the retarding force exerted by the viscous damper is directly proportional to the rotational speed of the reel. Accordingly, the reel will tend to seek a velocity at which the retarding force is equal to the force exerted on the reel by the torsional spring, such that the spool will attain a constant velocity. The viscous damper disclosed in Rader, however, is rigidly attached to the support shaft and therefore exerts a retarding force on the hose reel irrespective of whether the hose is being payed-out or being retracted. In most applications, it is not necessary to regulate the speed at which the hose is payed-out. Accordingly, a viscous damper that operates in both directions such as disclosed by Rader unnecessarily loads the hose as it is being payed-out, potentially leading to premature failure of the hose and/or the rewind mechanism. Accordingly, what is needed is a take-up reel with a viscous clutch that operates only when the hose is being retracted and allows the hose reel to be decoupled from the viscous dampener when the hose is being payed-out.
The present invention satisfies the foregoing need by providing a hose reel assembly having a unidirectional viscous damper assembly. In the illustrative embodiment, the unidirectional viscous damper assembly consists of a viscous clutch and a unidirectional clutch. The viscous clutch is operatively coupled between the hose reel and the stationary support by means of the unidirectional clutch that engages the viscous clutch only when the hose reel is rewinding, not when the hose reel is paying-out the hose. The take-up reel comprises a stationary support shaft attached to a frame and a unidirectional clutch assembly supported for rotation by the stationary support shaft. The unidirectional clutch assembly is capable of rotating freely in one direction about the stationary support shaft but engages the stationary support shaft to prevent rotation in the opposite direction. The unidirectional clutch, in turn, is secured to a plurality of stator disks of a multidisk viscous clutch. The rotor disks of the viscous clutch, in turn, are coupled to the hose reel. A chamber filled with a viscous fluid encloses the stator and rotor disks. The viscous fluid provides a shearing action to retard the relative motion between the stator disks attached to the unidirectional clutch assembly and the rotor disks attached to the hose reel. The multi-plate construction of the viscous clutch provides a highly efficient and compact retarding mechanism. A conventional torsional spring provides a biased urging the reel to fully rewind the hose wound thereon.
In operation, as the hose is payed out, a shearing force develops between the rotor disks coupled to the hose reel and the stator disks coupled to the unidirectional clutch. The shearing force exerts a slight torque on the unidirectional clutch causing the unidirectional clutch to disengage and freewheel about the stationary support shaft. Thus, the only resistance force exerted by the viscous clutch assembly opposing this direction of motion is the torque necessary to overcome the friction inherent in the unidirectional clutch. Conversely, when the reel is being retracted under the urging of the torsional spring, a shearing force is developed between the rotor disks attached to the hose reel and the stator disks attached to the unidirectional clutch. In this direction, however, the unidirectional clutch engages the stationary support shaft thereby preventing rotation of the stator disks. The shearing force developed between the now static stator disks and rotor disks is proportional to the relative velocity between the stator disks and the rotor disks. Accordingly, as the rewind velocity of the hose reel builds, a counteracting torque is developed by the shearing of the viscous fluid between the stator and rotor disks until at a certain velocity, the forces balance and the hose reel attains a steady-state velocity. The steady-state velocity may be adjusted by, among other things, adjusting the viscosity of the fluid in the viscous clutch and/or varying the number of stators and rotors and their relative spacing.
By providing a uni-directional viscous clutch that acts to retard only the take-up velocity of the hose reel, it is possible to provide an apparatus that permits the hose to be payed-out at any speed without resistance from the viscous clutch while providing the substantial benefits of a viscous speed governor during take-up. The invention thus provides all of the safety benefits of a viscous speed governor without the unnecessary wear and tear inherent in a conventional bi-directional viscous clutch.